Nitrogen-doped carbon nanosheets with Fe-based nanoparticles for highly efficient degradation of antibiotics and sulfate ion enhancement effect

Selective removal of organic contaminants and ascorbic acid enhancement effect based on the magnetic Fe0/FeS2-doped carbon nanolayer

Developing highly effective iron-based catalyst to selectively remove organic contaminants has garnered considerable attention. Herein, a magnetic Fe0/FeS2-doped carbon nanolayer (S-Fe@NC) was synthesized through a straightforward one-step pyrolysis method, pyrolyzing a mixture composed of 4,6-dihydroxypyrimidine, trithiocyanuric acid, and FeCl3·6H2O. With the presence of PMS, S-Fe@NC demonstrated the ability to remove almost 100% bisphenol-A (50 μM) within 3 min, attributed to its excellent graphitization degree and high FeS2/Fe0 content. Furthermore, the S-Fe@NC catalyst demonstrated an impressive kobs value of 1.476 min-1, which surpassed the traditional Fenton system by 77 times and even exceeded the commercial Fe0 catalyst by 127 times. More importantly, the S-Fe@NC/PMS system succeeded in selectively removing organic contaminants based on the hydrophobic interaction between catalyst and contaminants. Besides, the result of electron paramagnetic resonance and the radical quenching experiments indicated that ·OH, SO4·-, 1O2, and O2·- were involved in the organic contaminants removal. Interestingly, after adding ascorbic acid (AA) to the S-Fe@NC/PMS system, more ROS could be generated to result in the kobs augmenting by 4.16 times (6.133 min-1), completely different from the common sense that AA was usually used as a radical quencher. Additionally, the magnetically separable catalyst also exhibited excellent reusability and broad pH adaptability (2.0-12.0). This study provided a valuable insight for developing highly selective and effective Fe-based catalyst for practical wastewater treatment.

Removal of tetracycline in aqueous solution by iron-loaded biochar derived from polymeric ferric sulfate and bagasse

In this study, the tetracycline (TC) removal performance of iron-loaded biochar (BPFSB) derived from sugarcane bagasse and polymerized iron sulfate was investigated, and the mechanism of TC removal was also explored by study of isotherms, kinetics and thermodynamics and characterization of fresh and used BPFSB (XRD, FTIR, SEM and XPS). The results showed that under optimized conditions (initial pH 2; BPFSB dosage 0.8 g·L-1; TC initial concentration 100 mg·L-1; Contact time 24 h; temperature 298 K), the removal efficiency of TC was as high as 99.03%. The isothermal removal of TC followed well the Langmuir, Freundlich, and Temkin models, indicating that multilayer surface chemisorption dominated the TC removal. The maximum removal capacity of TC by BPFSB at different temperatures was 185.5 mg·g-1 (298 K), 192.7 mg·g-1 (308 K), and 230.9 mg·g-1 (318 K), respectively. The pseudo-second-kinetic model described the TC removal better, while its rate-controlling step was a combination of liquid film diffusion, intraparticle diffusion, and chemical reaction. Meanwhile, TC removal was also a spontaneous and endothermic process, during which the randomness and disorder between the solid-liquid interface was increased. According to the characterization of BPFSBs before and after TC removal, H-bonding and complexation were the major interactions for TC surface adsorption. Furthermore, BPFSB was efficiently regenerated by NaOH. In summary, BPFSB had the potential for practical application in TC removal.

Performance and mechanism of sycamore flock based biochar in removing oxytetracycline hydrochloride

In this study, sycamore flocs (SF), which caused environmental and health problems, were utilized to prepare biochar. SFB_2-900 obtained under the conditions of activation agent K₂CO₃, pyrolysis temperature 900℃ and m(K₂CO₃):m(BC) 2 had the strongest adsorption capacity (730 mg/g) for oxytetracycline hydrochloride (OTC-HCl). The pseudo-second-order kinetic model and Langmuir model described the adsorption kinetics and isotherms best. SFB_2-900 exhibited high OTC-HCl adsorption capacity in both higher ionic strength and wide pH range. The theoretical simulation indicated that the closest interaction distance between OTC-HCl and SFB_2-900 was 2.44 Å via π-π stacking configuration. Pore filling, π-π electron donor acceptor (EDA) interaction, H-bonding and electrostatic interactions were also involved in the process of OTC-HCl removal. SFB_2-900 showed great removal efficiency for OTC-HCl in different water matrices and good regeneration ability. This study solved the problems caused by SF, realized waste biomass recycling, and achieved preparing high-efficient adsorbent for antibiotic.